Not applicable.
The present invention relates to optical switching devices and, more particularly, to optical devices for selectively redirecting light as a function of its polarization state.
Optical wave or wavelength division multiplex (WDM) systems utilize multiplexing to transmit a plurality of optical signals over a single optical fiber. The bandwidth of the optical fiber is divided into several wavelength bands each occupied by a single carrier signal or channel modulated by one or more information signals. As a result, several information signals can be transmitted over a single optical fiber. Early WDM systems took advantage of two major windows in the optical fiber for transmission of two channels. More recently, so-called coarse and dense wavelength division multiplex (DWDM) systems have multiplexed nearly 100 channels with data rates approaching 2.5 Gbits per sec. on a single fiber.
While WDM provides a mechanism for more effective utilization of the available bandwidth of the optical fiber, multiplexing, demultiplexing, and routing individual optical signals require the development of fast, efficient optical switching and filtering devices. A multiplexer utilizes switching devices in an xe2x80x9caddxe2x80x9d device to combine multiple individual channels (each defined by its own wavelength spectrum) into a single WDM signal. On the other hand, demultiplexing is the process of separating or dropping individual channels from the composite WDM signal and coupling the individual channels to specific outputs for further processing. Routing is the process of permuting an input channel to a selected output port in response to a control signal imposed on a switching device.
Optical multiplexing and demultiplexing have been performed with prisms to combine and separate light of individual colors in a multiplexed signal. In addition, filters based on fiber Bragg gratings (FBG) and array waveguide-gratings are used as add and drop wavelength filters. The filters are typically switched in and out of the optical path of the signals using electro-optical modulation techniques.
What is desired is a switching device providing rapid, efficient, and reliable wavelength specific, optical switching.